# PostgreSQL 9.1 → 9.2 GUC diff

> Core configuration parameters added, removed, or changed in boot default between PostgreSQL 9.1 and 9.2.
---

> [!NOTE]
> **Fact.** The measured inventory changes from 219 to 224 settings: 8 added, 4 boot-default changes, and 3 removed.

## Added parameters {#added}

| Parameter | Type | Context | Boot default | Category |
| --- | --- | --- | --- | --- |
| [`enable_indexonlyscan`](/parameters/enable-indexonlyscan/) | `bool` | `user` | `on` | Query Tuning / Planner Method Configuration |
| [`event_source`](/parameters/event-source/) | `string` | `postmaster` | `PostgreSQL` | Reporting and Logging / Where to Log |
| [`ssl_ca_file`](/parameters/ssl-ca-file/) | `string` | `postmaster` | `""` (empty string) | Connections and Authentication / Security and Authentication |
| [`ssl_cert_file`](/parameters/ssl-cert-file/) | `string` | `postmaster` | `server.crt` | Connections and Authentication / Security and Authentication |
| [`ssl_crl_file`](/parameters/ssl-crl-file/) | `string` | `postmaster` | `""` (empty string) | Connections and Authentication / Security and Authentication |
| [`ssl_key_file`](/parameters/ssl-key-file/) | `string` | `postmaster` | `server.key` | Connections and Authentication / Security and Authentication |
| [`temp_file_limit`](/parameters/temp-file-limit/) | `integer` | `superuser` | `-1 kB` | Resource Usage / Disk |
| [`track_io_timing`](/parameters/track-io-timing/) | `bool` | `superuser` | `off` | Statistics / Query and Index Statistics Collector |
{.full-width}

## Boot-default changes {#default-changes}

| Parameter | PG9.1 | PG9.2 | Category |
| --- | --- | --- | --- |
| [`TimeZone`](/parameters/timezone/) | — (not set) | `GMT` | Client Connection Defaults / Locale and Formatting |
| [`log_timezone`](/parameters/log-timezone/) | — (not set) | `GMT` | Reporting and Logging / What to Log |
| [`server_version`](/parameters/server-version/) | `9.1.24` | `9.2.23` | Preset Options |
| [`server_version_num`](/parameters/server-version-num/) | `90124` | `90223` | Preset Options |
{.full-width}

## Removed parameters {#removed}

| Parameter | Last type | Context | Last boot default | Category |
| --- | --- | --- | --- | --- |
| [`custom_variable_classes`](/parameters/custom-variable-classes/) | `string` | `sighup` | — (not set) | Customized Options |
| [`silent_mode`](/parameters/silent-mode/) | `bool` | `postmaster` | `off` | Reporting and Logging / Where to Log |
| [`wal_sender_delay`](/parameters/wal-sender-delay/) | `integer` | `sighup` | `1000 ms` (1 s) | Replication / Master Server |
{.full-width}

## Method {#method}

The three lists compare the pinned PG9.1 and PG9.2 `pg_settings` snapshots directly. A default change is a change in the `boot_val` plus `unit` pair; `setting` is excluded so an `initdb`-generated value is not mistaken for the compiled boot default.

- [Machine-readable diff data](/data/diffs.json)
- [Complete GUC JSONL](/data/guc.jsonl)